Introduction of the IP multimedia subsystem (IMS) into mobile networks based on 3rd Generation Partnership Project (3GPP) offers the possibility to route a session from a calling party to a called party using Internet Protocol (IP) connectivity. Assuming the calling party roaming from its home communication network to a serving or visited communication network, signaling data and media data of an originating session of the calling party are routed from the serving communication network of the calling party to the home communication network of the calling party and thereupon further to the serving communication network in which the called party resides.
Recently, efforts in optimizing routing the session from a calling party located in its serving communication network to a called party has resulted in routing the media data of a session from the calling party to the called party directly via the serving communication network of the calling party. Such media routing optimization is known for “local break out” calls for which the media data of the call are not forced back to the home communication network of the calling party but is routed to the called party via the serving communication network of the calling party. Further, media routing optimization may be enabled by Optimized Media Routing (OMR) aiming at routing the media data of a session directly via the serving communication network of a calling party without passing the home communication network of the calling party.
Referring to FIG. 1, an IMS based communication system 100 for routing an originated voice session from calling party 102 located in its serving or visited communication network 104 to a called party is illustrated. A session path of signaling data 106 of the session runs from the serving communication network 104 of the calling party 102 to the home communication network 108 of the calling party 102 and then, for example, to a home communication network of the terminating called party. In this embodiment, the serving communication network 104 of the calling party 102 corresponds to the Visited Public Land Mobile Network (VPLMN), and the home communication network 108 or the calling party 102 corresponds to the Home Public Land Mobile Network (HPLMN). A session path of media data 110 of the session runs to the called party via the serving communication network 104 of the calling party 102 and accordingly bypasses media routing nodes of the home communication network 108 of the calling party 102. In case the called party has also roamed to its serving or visited communication network, the signaling data 106 and media data 110 of the session are routed from the home communication network of the calling party to the serving communication network of the called party.
In the serving communication network 104, the signaling data 106 pass firstly a Serving and Packet Data Network (PDN) Gateway (S&P GW) 112, then a Proxy-Call Session Control Function (P-CSCF) 114, and an Interconnection Boarder Control Function (IBCF) 116. Further, in the home communication network 108, the signaling data 106 of the session pass firstly an IBCF 118, then a Serving-Call Session Control Function (S-CSCF) 120, a Service Centralization and Continuity Application Server (SCC AS) 122, and then a network interconnection node 124 or 125. The interconnection node 124 comprises an IBCF 126 configured for routing signaling data. The interconnection node 125 is configured as a Breakout Gateway Control Function (BGCF) 127 configured for routing a session to a Mobile Switching Center-Server (MSC-S) or a Media Gateway Control Function (MGCF) of a core network of the home communication network 108 for breaking out the session from the IMS based home communication network 508 to a circuit switched (CS) communication network. The MSC-S and the MGCF are denoted together by a reference numeral 128. A determination of a selection of one of the interconnection nodes 124 and 126 is executed by the S-CSCF 120 of the home communication network 108 of the calling party 102.
The media data 110 of the session are routed via the serving communication network 104 of the calling party 102 passing the S&P GW 112, and an Access Gateway (AGW) or an Access Transfer Gateway (ATGW), both being denoted by a reference numeral 130. A decision whether to route the media data 110 via the serving communication network 104 is also executed in the home communication network 108.
The session routing path of the signaling data 106 is enabled by locally breaking out the session. Here, a location of the PDN Gateway 112 in the serving communication network 104 of the calling party 102 determines to execute a local breakout of the call.
For completeness, a visited Policy and Charging Rules Function (vPCRF) 132 is located in the serving communication network 102, and a home Policy and Charging Rules Function (hPCRF) 134, an Interrogation Call Session Control Function (I-CSCF) 136, a Home Subscriber Server (HSS) 138, an Electronic Numbering Function ENUM 140, a Media Gateway (M-MGW) 142, and a Translation Gateway TrGW 130 in the home communication network 108.
Charging or payment of the session is based on the session routing path of the signaling data 106.
Accordingly, routing an originating session of a calling party having roamed to its visited communication network to the called party via the IMS based home communication network of the calling party may be particularly complex and network capacity consuming, since the signaling data and the media data of the session may not be routed along with one another, and respective routing decisions may be executed in the home communication network. Further, from a session charging perspective of view, mobile operators operating a serving communication network of the calling party may not substantially participate in charging an originating session of a calling party.